What is NKH (nonketotic hyperglycinemia)?

Nonketotic hyperglycinemia, often shortened to NKH and also called glycine encephalopathy, is a genetic condition. Every cell relies on a set of enzymes called the glycine cleavage system to break down glycine once the body is finished with it. In NKH, that system works poorly or not at all, so glycine piles up in the blood and, most harmfully, in the brain.

Glycine also acts as a chemical messenger between brain cells. When there is far too much of it, brain signaling is disrupted. That's why NKH can cause extreme sleepiness and breathing trouble in newborns, followed by hard-to-control seizures, low muscle tone, feeding difficulties, and profound developmental delays.

For the O'Sullivan family, NKH is not a textbook term. Their son Drake was diagnosed at about two weeks old in 2016, and their daughter Vivian was diagnosed within hours of her birth in 2019. Both live with the severe form today. As their mom, Tarah, puts it: "Rare should not mean disposable. Rare should not mean not valuable."

There is no approved treatment that fixes the root cause of NKH. That is why the Drake Rayden Foundation is helping fund a one-dose gene therapy trial. You can read Drake and Vivian's story or help close the final gap.

Sources: MedlinePlus Genetics: Nonketotic hyperglycinemia · GeneReviews (NCBI): Nonketotic Hyperglycinemia · NORD: Nonketotic Hyperglycinemia